Eductor pumps, also referred to as jet pumps, typically include a body that has a motive fluid inlet section with a motive fluid nozzle disposed therein. The eductor body also defines a mixing chamber positioned downstream of the motive fluid nozzle. The mixing chamber also includes a solids inlet port for supplying solids such as bottom ash, fly ash, pyrites or other solids into the mixing chamber. The solids inlet port is typically positioned on an upper portion of the mixing chamber so that the solids can be gravity fed into the mixing chamber from a hopper. The eductor pump also includes a venturi or diffuser that consists of an inlet nozzle, a throat section and a discharge nozzle. The educator and the components thereof have predetermined optimal contours, dimensions and shapes to attain design flow and velocity requirements of the fluids and solids flowing therethrough.
A fluid flowing through the motive fluid nozzle is discharged into the mixing chamber in a high velocity jet stream and creates a suction pressure in portions of the mixing chamber around the jet stream. However, fluids in other portions of the eductor, for example in the motive fluid nozzle and in portions of the diffuser can be 150 psi or more. As a result, the solids that are fed into the mixing chamber by gravity feed and assisted by the suction pressure are entrained in the jet stream and are subsequently ejected into the diffuser. A mixture of the solids and the motive fluid are discharged from the discharge nozzle of the diffuser to a suitable holding area.
During operation the fluids and solids flow through the eductor under pressure. The bottom ash, fly ash, pyrites and other solids conveyed in the eductor are generally abrasive and can cause sliding and impact erosion of internal surfaces of the eductor. The eductors and components thereof are typically manufactured as one integral unit, for example a single casting, from a metal alloy that is abrasive resistant and capable of withstanding the operating pressure. However, over time, the eductor and components thereof wear causing the predetermined contours, dimensions and shapes change and degradation. As a result, the design flow and velocity requirements of the fluids and solids flowing through the educator can no longer be attained. To remedy the wear problems, the entire single unit educator must typically be replaced at a significant cost.